Do Vaccines Cause Autism in Dogs?

IntroductionBefore training as a veterinarian, I studied animal behavior. I worked with primates, and one of the most fascinating aspects of these animals was the deep similarity between their behavior and that of humans. Such similarities shouldn’t be surprising, of course, because we share many of the mechanisms that produce our behavior. Evolution has produced brains and sense organs and various anatomical and physiological systems for generating behavior, and many of these systems are shared between species. The more closely related, in evolutionary terms, the species are, the more such behavior-generating mechanisms they share, and the more similar their behavior is likely to be.

This, of course, applies to all species, not just between humans and other primates. It is not difficult to find great behavioral similarity among mammals, even between relatively distantly-related groups such as human and our canine and feline companions. The similarities may be fewer and the differences more noticeable, but we still share much of our basic biology, including the mechanisms that generate behavior, and we exhibit many behaviors that appear similar in form and function.

One major challenge in studying animal behavior is how to choose our terminology. Many of the words describing behavior in humans contain explicit or implicit information about mental states. If I say someone is angry or afraid, I am describing their feelings and internal experience directly, and presuming it conforms to general human patterns. But if I say someone is “cowering from her” or is “pummeling his face,” these descriptions of behavior contain implied mental states, of fear and anger respectively. So when we describe the behavior of animals, how do we handle the explicit or implicit attribution of mental states that we cannot verify are present or the same as those in humans when animals cannot verbalize their feelings and agree on appropriate descriptive terms? Should we avoid assuming mental states like our own, and if we should how do we accomplish this using language that so often contains implicit attribution of such mental states?

There is no simple solution to these questions. We can try to describe all behaviors mechanically, in terms of specific body movements, but that is cumbersome and arguably misses important and obvious attributes of the behavior. A dog and cat may both wag their tails, but the likely response if you persist in doing whatever you did to start the tail wagging is likely to be very different. The dog might well lick your face while the cat might as likely scratch it! Saying that the dog “wagged his tail playfully” and the cat “flicked her tail irritably” implies mental states we cannot absolutely verify, but these descriptions are a lot more useful and predictive of future behavior.

Some people object to at least some use of terms connoting mental states to dogs and cats because we cannot know their feelings with certainty, and because there are obvious cognitive differences between humans and our pets that influence the kinds of mental states we think it likely dogs and cats can have. There is, of course, a matter of degree in this. If we say “the dog is afraid” or “the cat is mad,” some people might object, but most would accept these terms as roughly appropriate. However, if say “the dog is skeptical” or “the cat is devout,” few people would accept those as legitimate because they imply thought processes we think our pets are unlikely to be capable of. There is, not surprisingly, a large grey area between these extremes.

There are pros and cons to using descriptions for feelings and behaviors in our pets that are commonly used to describe such feelings and behaviors in people. On one hand, we risk anthropomorphism, the attribution of human feelings and motivations to non-human animals. For example, people often describe their dog as looking “guilty” when he or she is punished for peeing in the house. It is unlikely, however, dogs, understand the kinds of obligations and social conventions required to feel guilty for violating a promise not to pee in the house. Thinking the dog can have this level of comprehension and the feeling of remorse can often lead owners to imagine intentions, a deliberate desire to defy the owner, that the dog also probably doesn’t have, which can negatively influence their bond with the pet and the way they try to alter the undesirable behavior.

Similarly, when a cat pees in the house while an owner is on a trip, the owner will often say the cat did it “because he was mad at me.” This generates a very different owner response than if we describe the behavior as “inappropriate urination associated with routine change: or something more emotionally neutral.

On the other hand, because humans share evolutionary relationships and many of the basic mechanisms of behavior with other animals, it is perfectly reasonable to assume significant similarity in the genesis of behavior and internal experiences. The presumption that humans are fundamentally, qualitatively different in every way from all other animals in their mental states or behavior is scientifically implausible, as well as being arrogant and self-serving. Mental similarities that correspond to similarities in behavior are a likely and parsimonious way of studying and characterizing animal behavior.

All of this is by way of introducing the real subject of this post, the question of whether dogs can fairly be described as “autistic” and, if so, whether we can blame this on vaccination

So Can Dogs Get Autism?This question was recently brought to my attention by some fellow skeptics who pointed me towards a dramatic and inflammatory article on an anti-vaccine web site.

As the title suggests, this article makes several claims about canine behavioral disorders and vaccines, which I will address individually:

Pets, especially dogs, exhibit behavioral disorders that share some features of Autism Spectrum Disorder (ASD) and may also share some underlying causal mechanisms

Vaccines in dogs cause a wide range of diseases, and among these is the appearance of abnormal behaviors following vaccination for rabies. These behaviors resemble autism in children.

Vaccination are required by law and given by veterinarians even when they are clearly not necessary. This is both very profitable and likely associated with the increase in autism-like behavioral pathologies in dogs.

Dogs Get Autism (or something like it)This seems to be the claim from this article that has struck skeptics as the most ridiculous or bizarre. The idea that dogs can get autism seems ridiculous on the face of it. However, part of the trouble here is the kind of issue of terminology I discussed earlier. ASD is challenging to define and identify in humans. Some of the characteristic symptoms relate to verbal and specifically human social behaviors. Since dogs cannot develop language and, obviously, are not human beings, they cannot be autistic if the word is strictly defined in terms of behaviors unique to the human species. Similarly, dogs cannot have Obsessive Compulsive Disorder (OCD), Panic Disorder, dementia, or any other psychopathology defined by behaviors or behavioral deficits unique to humans. Carried to a logical extreme, if one cannot be definitively said to experience fear, anger, sadness, or other emotions without verbally acknowledging these feelings or exhibiting them in characteristically human ways, then dogs cannot be described as having any of these feelings either.

However, dogs do share anatomic and physiologic mechanisms for generating their behavior that are homologous (meaning derived from the same evolutionary precursors and processes) to those which generate our behavior. And dogs do exhibit behaviors that look very much like fear, anger and sadness, as well as constellations and patterns of behavior that look very much like OCD, Panic Disorder, dementia, and ASD. Whether or not we choose to use the same descriptive terms for these behaviors depends more on our purposes and our concerns about the impact of this terminology on how others receive our arguments than on the question of whether the behaviors and their biological antecedents are related, which they very likely are.

The claim that dogs exhibit ASD-like behaviors is supported by citing the work of Tufts University veterinarian and behaviorist Dr. Nicholas Dodman. Dr. Dodman has published both research articles and popular books about animal behavior, and he frequently makes direct and explicit comparisons between clinical behavioral pathologies in humans and similar patterns of behavior in animals. The specific article cited in the Vaccine Reaction piece was a popular piece by Dr. Dodman in the magazine Psychology Today, Can Dogs Have Autism? Dr. Dodman addresses this question in a more academic manner through a number of scientific reports (e.g. 1, 2). He has also studied a number of other behavioral pathologies in dogs and other species which he suggests may have meaningful similarities to OCD and Tourette’s syndrome.

I have mixed feelings about Dr. Dodman’s use of human diagnostic terminology in reference to behavior problems in non-human animals. I agree that there are striking similarities in some of the patterns of behavior he identifies, and I think investigating potential shared causal mechanisms is worthwhile. To the extent that animal models of human disease share manifestations and causal mechanisms, identifying them can improve our understanding of these diseases in humans as well as the model species. This is a standard part of medical research, and there is no fundamental reason it shouldn’t be applied to behavioral disorders.

I also think that by communicating with the general public about this kind of research can generate better public understand and support for the research and for science generally, which is desperately needed now more than any time in the past century. Dr. Dodman has had great success in sharing his passion and the subjects of his research with the public, and I think that is worthwhile even if not every hypothesis he comes up with ends up being correct.

However, I also recognize the dangers of labeling non-human behavioral disorders with diagnostic labels developed for use in people. Even when there are shared features and casual mechanisms involved, there are also meaningful differences between the human disorders and those seen in other species. A key feature in many cases of ASD, for example, involves abnormalities in language development. This is a core aspect of human behavior, and a large part of the real-world problems an ASD diagnosis creates for patients and their families. Identifying tail-chasing in bull terriers as “autism” runs the risk exaggerating or oversimplifying the similarities between the disorders, which can interfere with full and accurate understanding of them. Such use of language can also be misinterpreted as demeaning to human ASD patients. Comparisons of stigmatized human groups to animals has long been a powerful weapon against these groups, and while I have no concern that Dr. Dodman has any such ill intent in his use of human diagnostic terms, I can see how his legitimate scientific background could appear to legitimize misuse or misinterpretation of his work by others.

That is, in fact, what has occurred in the Vaccine Reaction article. While the reference to Dr. Dodman’s work on ASD-like behavior in dogs is generally accurate, it is juxtaposed to completely inaccurate claims about vaccines, including the claim that they are a causal agent in ASD. This implies that Dr. Dodman’s work supports a link between vaccination and ASD or other behavioral pathology, which it most absolutely does not.

On balance, I don’t believe the claim that dogs can get autism is as unreasonable or prima facie ridiculous as it seems to some people. I think he has some evidence to support meaningful similarities between some canine behavioral pathology and ASD, and I think further investigation of these similarities could possibly lead to better understanding of the causes and mechanisms of ASD. However, I also believe that there are important differences between canine and human cognition and behavior that mean humans and dogs cannot both be “autistic” in precisely the same sense. An animal model of a human disease is, for all its usefulness, a model, not the disease itself, and there are always differences that matter.

I see both the advantages and disadvantages to using a shared term to describe similar, and potentially causally related, behavioral disorders in humans and dogs. To some extent, it may be fair to say that dogs get autism, but when exploring the meaning of this label more fully we must acknowledge and bear in mind the differences between the species as well so we aren’t misled by a simplistic or excessive concept of equivalence between human and canine behavioral disorders.

Vaccines Cause All Sorts of Diseases, Including Rabies-like Behavior or Canine AutismMy response to this claim is far less complex and nuanced: bullshit!

To expand on that further would require rehashing lots of subjects I’ve written about before. Instead, I will say only that while vaccines can cause both minor and serious adverse effects, they do so rarely, their benefits far outweigh their risks in most cases (for core vaccines, such as rabies, for example), and there is no such thing as “Rabies Miasm,” “Chronic Rabies” or “Canine Autism” that can be blamed on rabies vaccination. Here are some posts dealing with these and other anti-vaccine claims in more detail:

VACCINES DON’T CAUSE AUTISM!!!

The evidence for this conclusion is overwhelming (e.g. 1, 2, 3). I contacted Dr. Dodman after seeing his work used to imply a causal relationship between autism and vaccines, and he was unequivocal in his response. He does not believe that vaccines are a cause of autism, in humans or in dogs, and he rejects any suggestion that his work might support this false claim.

More Vaccines = More Autism in DogsBullshit redux. It is not even clear that dogs are being vaccinated more than in the past. Recent changes in our understanding of the average duration of immunity and other variables have led many vets to change vaccination practices, so quite a few of us are actually vaccinating less than we used to. There certainly are too many vets who haven’t kept up with the science in terms of vaccinating more than is necessary to provide protective immunity for some diseases, and revenue is likely one of many factors in this. Between changes in vaccination protocols and hesitancy about vaccination on the part of pet owners, it is as likely that vaccination rates have declined rather than increased in the last decade. However, I am not aware of any reliable data on this subject, and none was provided in the Vaccine Reaction article. Regardless of whether vaccination of dogs is increasing or declining, there is no evidence that vaccines are related to behavioral pathology in dogs, ASD-like or otherwise, and this is just another of the many false claims made in the article.

Bottom LineThere are behavioral disorders in dogs that share symptomatic and possibly causal features of behavioral disorders in humans. While the use of human diagnostic terminology in dogs is problematic, it is not unreasonable to suggest dogs may have behavioral syndromes similar in symptom pattern and causal factors to autism and other human disorders. Animal models of human disease are an established and useful element of medical research, and this can be reasonably applied to behavioral disorders if done judiciously. Dogs clearly do not get autism as it is defined and exhibited in humans, but they may well have related disorders that can provide insight into the causes and treatment of autism in humans.

Regardless of whether or not we choose to call similar or related disorders in dogs and humans by the same name, we can at least be confident of one key fact:

3 Responses to Do Vaccines Cause Autism in Dogs?

It depends. Most rabies virus vaccines are killed. MLV rabies vaccines exist but are not widely used since they have some risks killed vaccines do not, and for rabies killed vaccines provide very good immunization (which is not true for some other diseases).

There is also a canarypox vectored rabies vaccine for cats, which includes a live vector for the killed rabies virus components. This stimulates good immunity while avoiding the need for adjuvants thought to increase the risk of vaccine-associated sarcomas. So technically, this is a MLV vaccine as well.